• Current Optics and Photonics
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• v.3 no.1
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• pp.72-77
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• 2019

This study was performed to analyze the optical aberrations of the cornea induced by myopic refractive surgery. Corneal total higher-order aberrations, spherical aberration and coma for 4-mm and 6-mm pupils were measured using a wave-front analyzer. The amount of aberrations of the oblate corneal optics by the achieved correction was found to be larger than for the prolate corneal shape with complete eye, in an emmetropia control group. The change in corneal shape acts as an optical factor that degrades the quality of the retinal image; it seems to be one of the important factors related to quality of vision.

• Journal of Digital Convergence
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• v.11 no.1
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• pp.315-320
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• 2013

We have investigated the variation of spherical aberration of the anterior and posterior surface in a Korean sample population with various age between 20 to 71 years old. We used Pentacam (Oculus Inc., Germany) to measure the corneal radius, asphericity, and spherical aberration of 290 patients with normal cornea. There were negative correlation between corneal anterior radius and spherical aberration(r = -0.22, p<0.0001), and, there were negative correlation between corneal posterior radius and spherical aberration(r=-0.27, p < 0.0001). There were positive correlation between anterior asphericity and spherical aberration(r = 0.24, p < 0.0001), however there were negative correlation between posterior asphericity and spherical aberration(r = -0.17, p=0.00288).The average of anterior spherical aberration and posterior spherical aberration was $0.482{\pm}0.099{\mu}m$ and $-0.098{\pm}0.029{\mu}m$. The average of spherical aberration was $0.385{\pm}0.097{\mu}m$. There were significant positive correlations between anterior spherical aberration and age(r = 0.227, p<0.0001), and there were positive correlations between posterior aberration and age(r = 0.349, p<0.0001). It is considered that this data can be used as basic information for furture studies for improving the quality of vision of modern human and, through the analysis of the spherical aberration of cornea was to provide a better understanding of the optical part of the Korean's eye.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.1
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• pp.111-120
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• 2014

Purpose: This study was to investigate changes in the thickness of cornea, curvature of cornea, and aberration depending on the water contents, materials, and refractive power of contact lens. Methods: The differences in the corneal thickness between pre- and post-wearing the lenses were compared using 5 kinds of lenses. The changes in the corneal thickness, the curvatures of the anterior and posterior cornea, and high order aberration (HOA) before and after wearing the lenses were investigated at the center of the cornea, and the different distance and the direction away from the center of the cornea. For the equipments of measurement, ORB ScanII (Bausch & Lomb Inc, ver 3.14) was used to measure the corneal topography and thickness, and Zywave (Bausch & Lomb Inc, ver 5.20) was used to analyze the high order aberration. Results: Five (S1, S2, S3, T1, T2) of the lens was used for this study, excluding the lens T2 lens has four lenses and the thickness of the corneal shape, but the impact is minimal. In the case of the hydrogel soft contact lenses (T2 lens) with low oxygen permeability, the corneal thickness showed distinct increasing patterns. The high order aberration and coma aberration were most changed in the silicon hydrogel toric lens, while the depth of anterior was most changed in the hydrogel toric lens. Conclusion: Among the 5 kinds of contact lenses with different water contents, materials, and refractive power used for this study, the corneal shape change was small for the lenses with an oxygen permeability (Dk) of more than 28, and the largest for the lenses with a very low oxygen permeability.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.2
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• pp.35-39
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• 2009

Purpose: In this study a program was developed to determine corneal aberrations using corneal shape of topographer and represented a wavefront and corneal aberrations using zernike polynomial. Methods: When the pupil size was 6 mm, we calculated new corneal shape data with zernike polynomials using corneal shape data of ORBSCAN topographer. We programmed the wavefront construction using ray tracing for corneal shape, then represented corneal aberrations having zernike polynomial with 6th order and 28 terms. Conclusions: We developed programs to determine a wavefront and corneal aberrations using corneal shape of ORBSCAN topographer. Theses results will be applied to a development of new topographer and prescription of contact lens and OK lens.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.4
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• pp.439-444
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• 2011

Purpose: To represent the shape of toric corea in the elliptical function for the determination of curvature distribution and lacrimal thickness between cornea and contact lens when the lens is fitted. Methods: Topography measurements of corneal curvature and curvature equation derived from the assumed elliptical function were evaluated using the Excel program which included the necessary equation derived. Results: Mathematical expressions for the cornea whose ribbon shaped-topography image, in which the center does not coincide with the corneal apex, can be determined. Conclusions: For the application where the higher accuracy on the cornea is not required, such as higher order aberration, the cornea cal be expressed in the simple elliptical function.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.2
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• pp.179-186
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• 2013

Purpose: To compare corneal asphericity, visual acuity (VA), and ocular and corneal higher-order aberrations (HOAs) between myopic refractive surgery and emmetropia groups. Methods: Twenty three subjects ($23.0{\pm}2.5$ years) who underwent myopic refractive surgery and twenty emmetropia ($21.0{\pm}206$ years) were enrolled. The subjects'criteria were best unaided monocular VA of 20/20 or better in both two groups. High and low contrast log MAR visual acuities were measured under photopic and mesopic conditions. Corneal and ocular HOAs were measured using Wavefront Analyzer (KR-1W, Topcon) for 4 mm and 6 mm pupils. Corneal asphericity was taken by topography in KR-1W. Results: There was no significant difference in VA between two groups under either photopic or mesopic conditions. In ocular aberrations, there were significant differences in total HOAs, fourthorder and spherical aberration (SA) for a 6 mm between two groups (p=0.045, p<0.001, and p<0.001, respectively). In corneal aberrations, there was a significant difference in SA for 4 mm (p=0.001) and 6 mm (p<0.001) pupils between two groups and there were statistically significant differences in total HOAs (p<0.001) and fourth-order aberrations (p<0.001) between two groups for a 6 mm pupil. There was a significant correlation in emmetropia between Q-value and SA in ocular aberrations for 4 mm and 6 mm pupils (r=0.442, p=0.004, and r=0.519, p<0.001) and in corneal aberrations for 4 mm and 6 mm pupils (r=0.358, p=0.023, and r=0.646, p<0.001). No significant correlations were found between Q-value and SA in refractive surgery group. Conclusions: VA in myopic refractive surgery is better than or similar to emmetropia. Nevertheless, the more increasing pupil size is, the more increasing aberrations are. Thus, it could have an influence on the quality of vision at night.